In conventional gasoline dispenser designs, electrical devices are integrated within hazardous areas of the dispenser including components that contain fuel. In such typical prior dispensers, electrical devices are either enclosed in explosion proof housings or isolated through use of intrinsically safe circuitry, in order to protect against the hazard of a spark igniting fuel vapors. Also, several known dispenser designs provide for placing the mechanical apparatus (flow meter) of a fuel meter in a hazardous or classified zone, and its associated electrical apparatus (such as an electrical pulser) in an unclassified zone. The two zones are separated by a vapor barrier provided by an air gap, and mechanical linkages are used to interconnect the mechanical and electrical portions of the fuel meter apparatus. As discussed below, there are many prior designs to safeguard gasoline dispensers against electrical ignition of gasoline vapors.
Mackie, U.S. Pat. No. 3,254,795, teaches in a fuel dispenser the elimination of conventional mechanical motion transmitting couplers, for permitting electrical switch contacts to be hermetically sealed as a safeguard against ignition of gasoline vapors, and so forth.
Schneckenburger, U.S. Pat. No. 2,573,112, teaches in a coin operated dispensing pump, the application of a pedestal mounted housing away from the gasoline dispenser housing, wherein the pedestal housing encloses all of the coin operated mechanisms for operating the gasoline pump. Electrical connections between the coin operated mechanisms and the electrical mechanisms of the gasoline pump are connected via wires contained in enclosed conduits.
Irie, U.S. Pat. No. 3,773,219, discloses a fuel dispensing system providing for preset control. The preset mechanisms are located in a remote control system away from the fuel handling mechanisms, permitting a reduction in the number of electrical wires required near the fuel handling portions of the dispenser, in turn permitting an explosion-proof housing to be inexpensively constructed for whatever wires may remain in the vicinity of the fuel handling area.
Greenwood, U.S. Pat. No. 3,871,505, discloses a gasoline dispenser including isolated compartments for a gasoline flow path, and for various electronic mechanisms of the dispenser. As indicated in column 2, lines 54 through 61, an upper compartment 11 for electronic mechanisms is isolated from a lower compartment 10 by a bottom plate within the upper compartment 11. A fiberoptic system is used to transmit signals from the fuel handling compartment 10 to the electronic compartment 11.
In Howard et al., U.S. Pat. No. 4,162,027, a device for transferring information from the liquid handling area of a gasoline dispenser to a remote location includes electro-optic means for converting mechanically recorded or generated information into electrical signals, which are passed through a barrier containing spark preventing resistors, into a remote location outside of the hazardous zone.
Swick, U.S. Pat. No. 4,576,312, discloses a multiple product dispenser including a plurality of hoses. The enclosure or housing for the dispenser is segmented into a number of individual enclosures isolated from one another but joined together to form the overall housing. A light housing 60 is shown at the uppermost portion of the overall housing. The light housing 60 is duplicated on the opposite side of the dispenser in mirror image. As shown in FIG. 5, located between the light housings 60 is a trough 59 which houses conduits 12 for delivering gasoline to the dispenser hoses 26. As described in column 5, lines 34 through 40, the configuration is such that the light housings 60 are spaced a short distance away from trough 59 to provide an air gap therebetween, for preventing volatile fumes from entering the light housings 60, where they may possibly be ignited by the electrical apparatus contained within the light housings 60. There is no communication, be it mechanical or electrical, between the light housings 60 and the juxtaposed trough 59.